The long term goal of this project is to understand how oligodendrocytes, the cells responsible for making the myelin that insulates axons in the central nervous system, arise from neural precursor cells. During development, rapidly dividing neural precursors produce first neurons and then oligodendrocytes. This process must be tightly regulated to ensure that sufficient numbers of oligodendrocytes are produced and to prevent neural precursors from dividing too much. Using zebrafish as a model system, this project combines in vivo time-lapse imaging and genetic analysis to investigate genes that are necessary to regulate formation of oligodendrocytes from neural precursors. In previous studies, we performed a screen for newly induced mutations that disrupt the number and distribution of oligodendrocytes, began to characterize how these mutations affect oligodendrocyte development and identified some of the mutated genes. During the new project period we will extend our investigation of neural precursor maintenance and oligodendrocyte specification by using time-lapse imaging and genetic analysis to test the roles of cell division orientation and Notch signaling in regulating formation of neural cell lineages. Specific Aim 1 will analyze neural precursor division patterns during neurogenesis and gliogenesis and test the requirement of atypical Protein Kinase C in maintaining self-renewing precursor divisions. Specific Aim 2 will investigate the role of Notch signaling in promoting oligodendrocyte specification. Specific Aim 3 will investigate the function of Fbw7, the recognition subunit of an E3 SCF ubiquitin ligase, and test the hypothesis the Fbw7 regulates oligodendrocyte specification by modulating Notch activity. Completion of these aims will greatly extend our understanding of the molecular mechanisms that maintain neural precursors and guide oligodendrocyte formation, facilitating effective design of therapies intended to treat developmental and degenerative myelin disease and nervous system injury.